'He's not the pope' ... John Hemming and Alastair Campbell. Photographs by David Sillitoe and Sarah Lee for the Guardian

On Monday, the Liberal Democrat MP John Hemming named Ryan Giggs as the footballer who had taken out an injunction. This week David Cameron announced a joint committee on privacy law, saying the current situation was "unsustainable" when tens of thousands of people on Twitter had named the footballer. Alastair Campbell, on his blog, was one of a number of people who criticised the MP. So, asks Emine Saner, why did Hemming decide to out Ryan Giggs?

John Hemming: My concern in raising the issue was so that we wouldn't have secret prosecutions of people like Giles Coren [the Times journalist who was identified as one of the Twitter users who had broken an injunction on the social media site]. My fundamental concern was about jailing people in secret.

Alastair Campbell: Do you seriously believe that arising out of the case of this footballer and all these people on Twitter saying who he was, that there was the remotest possibility of anybody going to jail and in secret?

JH: The secrecy is certain, that is the way the procedures operate. I had another case earlier this year, involving Vicky Haigh [Hemming named her, using parliamentary privilege, after she was threatened with jail by Doncaster council for speaking at a meeting in parliament]. There was a case today, which involved attempting to get somebody put in jail in secret, with the identity of the parties not being known, with a hearing the press are not allowed to attend, which is exactly the same.

AC: My point is that those who were naming the footballer were doing it in breach of an injunction. Surely your job, as a parliamentarian, is to be part of a process that sees the law is upheld and in our system we have judges who interpret the law? And yet you chose to stand up in the House of Commons and allow the tabloid press in particular to open the floodgates, for what? This is not the Trafigura case [the company took out a superinjunction banning publication of a report relating to its toxic waste dumping], we're talking about the sex life of a footballer. I'm interested in your position as a parliamentarian and whether as a fundamental principle you accept the rule of law and the independence of the judiciary.

JH: I do.

AC: There has been a process to erode that, not out of some issue of great public interest, but because certain newspapers fear they will go to the wall unless they preserve their right to cover their front pages with stories about the sex lives of celebrities. There is no great issue of principle. All this nonsense about freedom of expression is about a certain section of our media fearing, under the influence of the internet, 24-hour news, that if they cannot get more and more of these stories they will go to the wall.

JH: I disagree, because I see a number of the other cases where you have information that is kept out of the public domain through the use of confidentiality orders.

AC: But why pick on this one? You must have known the impact you were going to have. Back in the days when I was a journalist there were very rare occasions when there was an injunction, but when there was, within the newspaper the lawyers would talk about it, the journalists would talk about it, we'd go home and talk to our families about it, they would talk to their friends about it. There has always been a group of people who will know about the issues underlying an injunction. All Twitter has done is accelerate the scale and speed of that. If that fundamentally changes the environment, then it's the job of parliament to decide whether you have to bring in a new system which makes sense of it. I am instinctively opposed to the whole notion of superinjunctions. My point is that an individual who happens to be a footballer uses the law as it exists. The judge grants an injunction. All you did was use parliamentary privilege to open the floodgates on this story. He's not the pope, he's not a politician, he's not the head of a corporation which is doing terrible things in Africa, he's a footballer who appears to have had an affair.

JH: If I hadn't done what I did on Monday, I accept that Sky wouldn't have just run with it as they did. We can't say what would or wouldn't have happened had I not spoken about the issue in the House. But I don't think I used parliamentary privilege in the sense that I needed to have it. The story had been printed in Scotland at the weekend, it had been all over Twitter and was on Wikipedia. It was in the public domain. Even though all speeches are privileged, I did not have to make use of privilege.

AC: Why didn't you do it outside parliament then?

JH: I hadn't thought about it at the time. What was at the top of my mind was concern about secret prosecutions. People have been gossiping about a footballer and the proposal is to get their details from Twitter and get a contempt of court action against them. There is not enough guidance as to how to approach contempt of court. You have to go into a contempt-of-court action on the assumption that you can get a jail sentence of up to two years. There has to be some clarity about what is going on.

AC: I totally agree.

JH: But that's not the system at the moment. I'm not talking about suing News Group, or Sky, or the BBC, we're talking about suing individuals.

JH: I personally think kiss-and-tell is tacky, so I have sympathy for him being on the receiving end of that.

AC: Do you agree that the reason why some of the newspaper groups are pushing so hard on this is not about freedom of the press, it's about their wish to be able to sell newspapers on the back of the sex lives of celebrities?

JH: I accept that some newspapers are more inclined that way than others, but I think there is a baby-and-bathwater situation. I have spoken to people who have been on the receiving end of these secret orders — I quoted one woman in my speech who said, "the process is terrifying. For the first two months I shook and I shake now in talking about it." This is somebody who has been through a secret hearing to do with a sex allegation and a celebrity . . . it's comparable to the Giggs saga. In this instance, she has to be anonymous. That's the sort of thing that is being done to people. I don't think, as a member of parliament, when I know what's going on, I should refuse to say anything about it.

• This article was amended on 28 and 31 May 2011. It originally stated that Giles Coren had been identified as one of the Twitter users naming Ryan Giggs. In fact, his actions relate to the case of a different footballer. In addition it said that John Hemming named Ryan Giggs as the footballer who had taken out a superinjunction. These have both been corrected.